丹酰-L-苯丙氨酸和L-苯丙氨酸对小牛肠碱性磷酸酶抑制作用动力学的比较性研究

利用紫外分光光度法揭示了丹酰-L-苯丙氨酸对小牛肠碱性磷酸酶的选择性抑制作用,并比较性地研究了丹酰-L-苯丙氨酸和L-苯丙氨酸对小牛肠碱性磷酸酶的动力学抑制过程.结果表明在37℃和碱性磷酸酶工作的最佳pH值(pH 10.4)的条件下,丹酰-L-苯丙氨酸与L-苯丙氨酸类似,能够有效抑制小牛肠碱性磷酸酶的活性;利用双倒数曲线拟合,判定丹酰-L-苯丙氨酸与L-苯丙氨酸的抑制类型均为反竞争性抑制,两者的抑制常数Ki均为mmol级.对丹酰-L-苯丙氨酸抑制小牛肠碱性磷酸酶的作用研究,不仪有助于进一步阐明L-苯丙氨酸埘组织特异性碱性磷酸酶的选择性抑制机理,而且丹酰基团的存在也为荧光标定碱性磷酸酶的特效抑制剂提供了可能.     

白首乌中C21甾苷对酪氨酸酶二酚酶活力的影响

测定滨海白首乌中有效成分C21甾苷对酪氨酸酶活性作用的影响.首乌C21甾苷经分离纯化后,得到的组分C21甾苷(Ⅲ)对酪氨酸酶二酚酶活性的抑制作用表现为可逆抑制效应.其对二酚酶的抑制作用显示浓度依赖关系,测定导致酶活力下降50%的抑制剂浓度(IC50)为0.078mg/mL,其抑制作用为竞争性抑制效应.     

外源植酸酶添加对土壤磷酸酶活性影响的荧光光谱法研究（英文）

外源植酸酶加入土壤中,能直接或者间接提高有机磷的生物有效性。但外源植酸酶添加后,对土壤本身的磷酸酶(单酯酶、二酯酶)活性会产生何种影响尚不明确。采用荧光物质为底物,将96微孔板和荧光检测法相结合,利用多功能酶标仪测定外源植酸酶(1g/50g干土)添加条件下红壤、棕壤以及褐土中磷酸单酯酶(酸性和碱性)和二酯酶的活性响应。结果表明,外源植酸酶添加后,酸性磷酸单酯酶活性在红壤中极显著增加(p≤0.01),而在褐土中显著降低;碱性磷酸单酯酶活性在棕壤和褐土中增加,其中在褐土中增加极显著(p≤0.01),而在红壤中显著降低;磷酸二酯酶活性在三种土壤中均不同程度地增加,其中在棕壤中增加极显著(p≤0.01);不同土壤中,培养到8天时不同酶活性亦保持增加,即红壤中的酸性磷酸单酯酶,棕壤中的磷酸二酯酶以及褐土中的碱性磷酸单酯酶分别保持活性增加,说明外源植酸酶的添加能够有效地增强土壤磷酸酶活性,这种作用不仅与土壤性质如pH和磷形态相关,并且可能与刺激微生物分泌酶量有关。运用荧光光谱法研究外源植酸酶对土壤磷酸酶活性的影响在国内外尚属首次。与传统的分光光度法相比,微孔板荧光法是一种灵敏、准确、快速、简便的土壤磷酸酶活性关系的测定方法。     

外源植酸酶添加对土壤磷酸酶活性影响的荧光光谱法研究

外源植酸酶加入土壤中,能直接或者间接提高有机磷的生物有效性。但外源植酸酶添加后,对土壤本身的磷酸酶(单酯酶、二酯酶)活性会产生何种影响尚不明确。采用荧光物质为底物,将96微孔板和荧光检测法相结合,利用多功能酶标仪测定外源植酸酶(1 g/50 g干土)添加条件下红壤、棕壤以及褐土中磷酸单酯酶(酸性和碱性)和二酯酶的活性响应。结果表明,外源植酸酶添加后,酸性磷酸单酯酶活性在红壤中极显著增加(p≤0.01),而在褐土中显著降低;碱性磷酸单酯酶活性在棕壤和褐土中增加,其中在褐土中增加极显著(p≤0.01),而在红壤中显著降低;磷酸二酯酶活性在三种土壤中均不同程度地增加,其中在棕壤中增加极显著(p≤0.01);不同土壤中,培养到8天时不同酶活性亦保持增加,即红壤中的酸性磷酸单酯酶,棕壤中的磷酸二酯酶以及褐土中的碱性磷酸单酯酶分别保持活性增加,说明外源植酸酶的添加能够有效地增强土壤磷酸酶活性,这种作用不仅与土壤性质如pH和磷形态相关,并且可能与刺激微生物分泌酶量有关。运用荧光光谱法研究外源植酸酶对土壤磷酸酶活性的影响在国内外尚属首次。与传统的分光光度法相比, 微孔板荧光法是一种灵敏、准确、快速、简便的土壤磷酸酶活性关系的测定方法。     

生物炭施用对土壤磷及磷酸酶活性影响的可见和荧光光谱法研究（英文）

含碳丰富的秸秆在无氧或限氧的条件下低温热解后得到生物炭可施入土壤,有利于缓解秸秆处理压力、减少污染、减少温室气体排放,并改良土壤。在重要的农粮基地辽宁潮棕壤上布置了生物炭还田试验。玉米田施用不同量的生物炭(0,360,1 800和3 600 kg·ha~(-1))一个生长季后,研究土壤有效磷(P)、有机P和全P含量的变化,并采用荧光共轭物质作为测定底物,通过酶解产生荧光物质研究土壤磷酸酶活性的响应。结果表明,生物炭添加到土壤后,土壤有效P含量随生物炭施用量增加而显著升高、有机P和全P的含量没有显著的变化。其原因是生物炭携带有效P而引起的。碱性磷酸单酯酶和磷酸二酯酶活性随生物炭添加量的增加而增大,适量生物炭处理(1 800 kg·ha~(-1))可显著增加酸性磷酸酶,而高量生物炭处理(3 600 kg·ha~(-1))对酸性磷酸酶略有抑制,可能是生物炭自身的偏碱性使土壤pH值增大所致。生物炭的添加对土壤磷素和磷酸酶活性的影响是土壤物理性质、化学性质及土壤微生物群落结构和代谢能力的综合体现,需要进一步深入研究。     

生物炭施用对土壤磷及磷酸酶活性影响的可见和荧光光谱法研究

含碳丰富的秸秆在无氧或限氧的条件下低温热解后得到生物炭可施入土壤,有利于缓解秸秆处理压力、减少污染、减少温室气体排放,并改良土壤。在重要的农粮基地辽宁潮棕壤上布置了生物炭还田试验。玉米田施用不同量的生物炭(0,360,1 800和3 600 kg·ha-1)一个生长季后,研究土壤有效磷(P)、有机P和全P含量的变化,并采用荧光共轭物质作为测定底物,通过酶解产生荧光物质研究土壤磷酸酶活性的响应。结果表明,生物炭添加到土壤后,土壤有效P含量随生物炭施用量增加而显著升高、有机P和全P的含量没有显著的变化。其原因是生物炭携带有效P而引起的。碱性磷酸单酯酶和磷酸二酯酶活性随生物炭添加量的增加而增大,适量生物炭处理(1 800 kg·ha-1)可显著增加酸性磷酸酶,而高量生物炭处理(3 600 kg·ha-1)对酸性磷酸酶略有抑制,可能是生物炭自身的偏碱性使土壤pH值增大所致。生物炭的添加对土壤磷素和磷酸酶活性的影响是土壤物理性质、化学性质及土壤微生物群落结构和代谢能力的综合体现,需要进一步深入研究。     

桑色素-Ce(Ⅳ)体系共振光散射法选择性测定小牛胸腺DNA

研究了桑色素与Ce(Ⅳ)反应形成的络合物与DNA作用的共振光散射(RLS)特征,发现小牛胸腺DNA(ctDNA)或鲱鱼精DNA(hsDNA)的加入都能使桑色素-Ce(Ⅳ)体系在320 nm处的共振光散射峰增强。在最优条件下,RLS强度与ctDNA的浓度在0～25 μg·mL-1范围内呈良好的线性关系,检出限为0.3 μg·mL-1;但是RLS强度对hsDNA的浓度却没有线性响应。并且,由于RLS强度对hsDNA浓度的响应值大大低于同浓度的ctDNA,因此可用于hsDNA存在下对ctDNA的选择性测定。将该法用于4种合成样的测定,回收率在93.7%～108.4%之间。     

污泥对土壤过氧化氢酶活性的影响

选取自来水厂污泥为实验样品,采用实验室模拟的方法研究了污泥对土壤过氧化氢酶活性及热力学特征参数的影响。结果表明：在不同污泥含量下所有测定期间内过氧化氢酶活性都呈现抑制作用,污泥含量越高,对过氧化氢酶的抑制作用越明显。含污泥的土壤从第1d到第7d,土壤酶活性迅速降低,表现出明显的抑制作用;在第7d,污泥对过氧化氢酶活性的抑制作用达到最大,之后过氧化氢酶的活性缓慢恢复,28d后酶活性趋于平缓。热力学研究表明,过氧化氢酶最适宜温度为307—327K。土壤中含污泥时所需的Ea和ΔH比CK高,且污泥含量越大所需的Ea和ΔH越高,说明酶促反应越来越困难。     

温度影响农药抑制植物酶的研究

为研制探测农药残留的生物传感器,本文研究了农药乐果对植物酶的抑制与温度的关系、植物酶反应的最适反应温度。从面粉中提取酶,采用分光光度法研究了乐果与面粉酶的抑制反应时间对酶活性的影响;研究了在同样温度时不同浓度,和相同浓度时不同温度的条件下,农药对植物酶活性的抑制情况。研究显示,抑制反应时间大于5分钟时,酶的活性明显地受到抑制;在48℃酶反应的速度最快;温度相同时受农药的抑制作用随农药的浓度增大而增强;随着温度的升高,一定浓度的农药对面粉酶的抑制变强。研究结果说明了研究微型恒温器的必要性。     

马铃薯中酪氨酸酶的提取及其活性的研究

采用缓冲溶液法提取马铃薯中的酪氨酸酶,以邻苯二酚溶液为底物,测定了不同体积的酶的活性,研究了在不同pH值、温度和无机盐的条件下对酶活性的影响,确定了酶活性的最适温度为40℃和最适pH值为6.78.     

Effect of calcium ions on the irradiation induced inactivation of cellulase

Abstract The activity of cellulase irradiated at various temperatures was examined as a function of irradiation dose. The effect of calcium ions in radiation inactivation of cellulase at irradiation temperature of 30°C was studied by using calcium sulfate. The calcium ions have a protective ability against radiation caused inactivation of cellulase by scavenging species such as OH(-) formed by irradiation of cellulase aqueous solution, in which the effective concentration range of the calcium ions was ～ 10(-3) M. The calcium ions do not act for the heat inactivation of the enzyme and the enzyme hydrolysis of filter paper or chaff as an activator because the calcium ions do not associate with the enzyme to form a calcium ion-enzyme complex.     

The Detection of Unfolding Intermediates of Soybean Lipoxygenase-1 during Urea Denaturation by Fluorescence Spectroscopy

The unfolding of soybean lipoxygenase-1 during urea denaturation has been followed by activity assays and fluorescence measurement. The presence of stable intermediates during unfolding for both ferrous and ferric forms of lipoxygenase-1 were observed. In the presence of 6.0 M urea, the unfolding of soybean lipoxygenase-1, as monitored by fluorescence intensity, is a triphasic process, while the inactivation of the enzyme shows a single-phase kinetics. The rate constant of inactivation is consistent with that of the fast conformational change of the enzyme. Based on these, a minimal scheme containing two intermediates was proposed to interpret the unfolding of lipoxygenase-1 induced by urea.     

Isotopic catalysis and isotopic analysis

Isotopes with magnetic nuclei accelerate the biochemical reactions of adenosine triphosphate synthesis by a factor of two to three. An isotope effect in which isotopes are preserved in the reaction system is known as isotopic catalysis. It has been revealed in enzymatic reactions catalyzed by magnesium, zinc, and calcium ions. Isotopic catalysis is sensitive to paramagnetic impurities, which inhibit it. It is shown that the presence of paramagnetic iron ions eliminates isotope effect and suppresses the isotopic catalysis of adenosine triphosphate synthesis.     

Effect Of Calcium Ions On The Irradiation Induced Inactivation Of Cellulase

Abstract

The activity of cellulase irradiated at various temperatures was examined as a function of irradiation dose. The effect of calcium ions in radiation inactivation of cellulase at irradiation temperature of 30°C was studied by using calcium sulfate. The calcium ions have a protective ability against radiation caused inactivation of cellulase by scavenging species such as OH^? formed by irradiation of cellulase aqueous solution, in which the effective concentration range of the calcium ions was ～ 10^?3 M. The calcium ions do not act for the heat inactivation of the enzyme and the enzyme hydrolysis of filter paper or chaff as an activator because the calcium ions do not associate with the enzyme to form a calcium ion-enzyme complex.     

Kinetics and mechanism of (salen)MnIII–catalysed hydrogen peroxide oxidation of alkyl aryl sulphides

The kinetics of (salen)Mn^III complexes catalysed oxidation of aryl methyl and alkyl phenyl sulphides with hydrogen peroxide have been investigated at 25°C in 80% acetonitrile – 20% water spectrophotometrically. The reaction follows first‐order kinetics in (salen)Mn^III complex and zero‐order kinetics in hydrogen peroxide. The order of the reaction with respect to sulphide is fractional and saturation in reaction rate occurs at higher sulphide concentrations. The pseudo first‐order rate constants have been analysed as per Michaelis–Menten kinetics to obtain the values of k₂, the oxidant‐substrate complex decomposition rate constant, and K, the oxidant‐substrate complex formation constant. The effects of nitrogenous bases, free radical inhibitor and changes in solvent composition have also been studied. A suitable mechanism, supported by electronic‐oxidant and electronic‐substrate effect studies, involving a manganese(III)‐hydroperoxide complex as reactive species has been proposed. Copyright © 2007 John Wiley & Sons, Ltd.     

金属-有机骨架[Zn(BDC)(H2O)2]n膜的原位制备及其对硝基苯类有机物的可逆检测

采用水热法,将锌片与对苯二甲酸(H2BDC)反应原位合成[Zn(BDC)(H2O)2]n薄膜.利用XRD和SEM分别对薄膜的结构、形貌和尺寸等进行了表征.结果表明,薄膜是由一维链状结构的金属-有机骨架材料纳米晶构成的,随着水热时间的增加,薄膜中的[Zn(BDC)(H2O)3]n纳米晶晶粒尺寸逐渐减小.该薄膜在紫外光的激...     

Thermal treatment alternatives for enzymes inactivation in fruit juices: Recent breakthroughs and advancements

Fruit juices (FJs) are frequently taken owing to their nutritious benefits, appealing flavour, and vibrant colour. The colours of the FJs are critical indicators of the qualitative features that influence the consumer's attention. Although FJs' intrinsic acidity serves as a barrier to bacterial growth, their enzymatic stability remains an issue for their shelf life. Inactivation of enzymes is critical during FJ processing, and selective inactivation is the primary focus of enzyme inactivation. The merchants, on the other hand, want the FJs to stay stable. The most prevalent technique of processing FJ is by conventional heat treatment, which degrades its nutritive value and appearance. The FJ processing industry has undergone a dramatic transformation from thermal treatments to nonthermal treatments (NTTs) during the past two decades to meet the requirements for microbiological and enzymatic stability. The manufacturers want safe and stable FJs, while buyers want high-quality FJs. According to the past investigation, NTTs have the potential to manufacture microbiologically safe and enzymatically stable FJs with low loss of bioactive components. Furthermore, it has been demonstrated that different NTTs combined with or without other NTTs or mild heating as a hurdle technology increase the synergistic effect for microbiological safety and stability of FJs. Concise information about the variables that affect NTTs' action mode has also been addressed. Primary inactivates enzymes by modifying the protein structure and active site conformation. NTTs may increase enzyme activity depending on the nature of the enzyme contained in FJs, the applied pressure, pH, temperature, and treatment period. This is due to the release of membrane-bound enzymes as well as changes in protein structure and active sites that allow substrate interaction. Additionally, the combination of several NTTs as a hurdle technology, as well as temperature and treatment periods, resulted in increased enzyme inactivation in FJs. Therefore, a combination of thermal and non-thermal technologies is suggested to increase the effectiveness of the process as well as preserve the juice quality.     

Cu(Ⅱ)离子对多巴色素作用的紫外-可见光谱研究

采用紫外 可见光谱法研究了在pH 6 5的缓冲溶液中Cu(Ⅱ )离子对多巴色素的催化作用。在通氮除氧的体系中 ,Cu(Ⅱ )离子显著加快多巴色素 (DC)于 4 75nm波长的褪色速度 ,并同时出现在 30 0～ 80 0nm波长范围内的全程吸收。实验结果表明 :Cu(Ⅱ )离子催化重排多巴色素生成的主要产物为 5 ,6 二羟基吲哚 2 羧酸 (DHICA) ,其反应前期对于DC为动力学一级反应 ;而且Cu(Ⅱ )离子可进一步催化 5 ,6 二羟基吲哚(DHI)和DHICA形成吲哚醌 (即吲哚 5 ,6 醌和吲哚 5 ,6 醌 2 羧酸 )的反应 ,吲哚醌一经生成 ,立即聚合形成黑色素。     

Enzymolysis kinetics and activities of ACE inhibitory peptides from wheat germ protein prepared with SFP ultrasound-assisted processing

There is a great demand for developing efficient enzymolysis methods in order to increase the enzymolysis efficiencies and activities of angiotensin converting enzyme (ACE) inhibitory peptides from wheat germ protein. The enzymolysis kinetics, ACE inhibitory activity of peptide and conversion rate of protein were studied using sweep frequency and pulsed (SFP) ultrasound-assisted enzymolysis and the results were compared with traditional enzymolysis. The studied factors were enzymolysis time and substrate concentration. By considering the activity of ACE inhibitory peptide and operation cost, the recommended conditions of SFP ultrasound-assisted enzymolysis were enzymolysis time of 120 min and substrate concentration of 24.0 g/L, which gave high conversion rates of protein (60.7%) and ACE inhibitory activity of peptide (65.9%). Compared to traditional enzymolysis, SFP ultrasound-assisted enzymolysis significantly increased the initial reaction rate (V) by 60.0% at substrate concentration of 24.0 g/L, increased the apparent breakdown rate constant (k(A)) by 66.7%, decreased the apparent constant (K(M)) by 6.9%, and raised the conversion rate of protein by 35.5% and ACE inhibitory activity of peptides by 35.6% under the recommended conditions. It has been concluded that SFP ultrasound can remarkably raise the enzymolysis efficiency and activity of ACE inhibitory peptides from wheat germ protein.